This removes the DarwinLog streaming support from debugserver, and the lldb API tests for it.
This was originally added by Todd Fiala via https://reviews.llvm.org/D22976 and follow on patches in 2016; the private calls it used to gather these logs did not work reliably and before it ever got completely debugged and stabilized, Todd left Apple and the code has been ignored ever since. The private calls it was using to gather this information have since ceased to exist.
It's an interesting bit of work, an interesting approach to specifying what log messages to surface back to the driver program, but having never been fully productized and used, it is completely broken by now. Every once in a while someone will stumble across this capability and try to use it, to much disappointment.
This removal is concentrating on the debugserver side of it. A lot of Todd's work in lldb is adding StructuredDataPlugin, source/Plugins/StructuredData/DarwinLog, EventDataStructuredData remains and should be removed but this quickly started getting a lot larger and I want to remove that in a separate patch when I have a little more time to look at it closely.